Mechanical screening, often just called screening, is the practice of taking granulated ore material and separating it into multiple grades by particle size. This practice occurs in a variety of industries such as mining and mineral processing, agriculture, pharmaceutical, food, plastics, and recycling.
The mining and mineral processing industry uses screening for a variety of processing applications. For example, after mining the minerals, the material is transported to a primary crusher. Before crushing large boulder are scalped on a shaker with 0.25 in (6.4 mm) thick shielding screening. Further down stream after crushing the material can pass through screens with openings or slots that continue to become smaller. Finally, screening is used to make a final separation to produce saleable products based on a grade or a size range.
A screening machine includes a drive that induces vibration, a screen media that causes particle separation, and a deck that holds the screen media and the drive and is the mode of transport for the vibration.
There are physical factors that make screening practical. For example, vibration, gravitational force, bed density, and material shape all facilitate the rate or cut. However, physical factors also can be the source of screening problems. Electrostatic forces, for example, can hinder screening efficiency by way of water attraction causing sticking or plugging, or very dry material can generate a charge that causes the material to attract to the screen itself. Different types of vibratory motion have their advantages and disadvantages. In addition media types also have their different properties that lead to advantages and disadvantages. Finally, because of the constant motion and vibration, maintenance and upkeep of the frame and support equipment which make vibratory screening possible can be challenging.
As shown in FIGS. 1 and 2, the screen deck assembly often is mounted on a frame that can include steel I-channel beams. More specifically, the screen deck assembly can be mounted atop steel coil springs that are positioned on the frame. A problem with this design arises when the coil springs become worn, broken, or otherwise need to be replaced. The entire screen deck assembly must be raised vertically a sufficient distance to allow the coil springs also to be raised vertically and removed from the guides on which the springs are mounted. Thus, there is a need in the industry for an alternative spring mounting design to make spring repair or replacement easier, faster, and less costly.